diff --git a/danmaku2ass.py b/danmaku2ass.py
index cc884ab..b5ba5ea 100755
--- a/danmaku2ass.py
+++ b/danmaku2ass.py
@@ -18,6 +18,8 @@ import xml.dom.minidom
 
 __all__ = ["Danmaku2ASS"]
 
+if sys.version_info < (3,):
+    raise RuntimeError('at least Python 3.0 is required')
 
 gettext.install('danmaku2ass', os.path.join(os.path.dirname(os.path.abspath(os.path.realpath(sys.argv[0] or 'locale'))), 'locale'))